Lead wire



April 15, 1941.

l J. H. RAMAGE 'LEAD WIRE Filed Deo.

IOO

INVENTOR f H. Pff/w16 BY/j/ l ATToRNE Patented Apr. 15, 19415 LEAD WIREJohn l-I. Ramage, Bloomfield, N. J., assigner, by mesnc assignments, toWestinghouse Electric and Manufacturing Company, East Pittsburgh, Pa.,'acorporation of Pennsylvania Application December 1, 1934, Serial No.755,550

8 Claims.

This invention relates to wires of such character as to be capable ofuse as leading-in conductors through the wall of a glass envelope andmore particularly to a leading-in wire for electrical devices.

Although the present invention may nd various uses in connection withelectrical devices where it is necessary to conduct current through thewall of a sealed container, it is particularly adapted for use as aleading-ln wire for incandescent electric lamps.

It is well recognized that a problem exists in providing an electricalconductor having the proper coeillcient of expansion so that, whensealed through the wall of a glass bulb, variations in the degree ofexpansion between the conductor and the glass will be reduced to aminimum or to such an extent as to prevent leakage.

It has been the practice for many years to use compound wiresV having 'acore of a base metal such as nickel-iron alloy and a covering or surface'coating of platinum or copper.

The use of copper-clad leading-in conductors has come into extensivepractice but the manufacture thereof is difllcult and costly since agreat deal of care must be taken in practicing the method of making sucha wire. When applying to the core the cover must be hermetically tight Yand diiliculty is experienced in obtaining the exactness and accuracyrequired in determining the diameter of the core and the cover.

It has been proposed to employ homogeneous wire of an alloy of chromiumand iron which,

however, did not give satisfactory results since it did not properlyadhere to the standard lamp glass and made a comparatively poor seal.The known alloys of iron and nickel behave in a similar manner and alsohave a great tendency to form air bubbles and air passages to the extentthat they are not usable without an outer coating of some glass wettingmaterial such as platinum or copper.

When using copper-clad wires, that is, a nickel iron core with a coppersheath, it has been the practice to employ a copper clad section of suchwire of sufilcient length to constitute the seal through the wall of theenvelope. To each end of this section of wire was welded another wire,one oi said wires constituted the lead which connected with the externalcontact of the lamp and the other the conductor connected with the lightsource. in the art as a three-piece weld, required a number ofoperations in its fabrication and, although it included only a smallportion of the copper clad This three-piece wire, which is knownleading-in wire including a combination of metals of such character asto meet the sealing-in requirements.

Another object of the invention is to provide a homogeneous wire whichmay be sealed through the wall of a bulb in the absence of air bubblesor voids between the glass and the wire when the wire is sealed throughthe glass wall.

A further object of the invention is to provide a leading-in wireincluding nickel, iron, and other ingredients in the form of an alloywhich wets with the glass to which it is sealed.

A still further object of the invention is to provide a leading-inconductor in the form of a homogeneous wire from which the occludedgases have been removed.

Other objects and advantages of the invention will be apparent from thefollowing description together with the accompanying drawing in which-Fig. 1 is a side view of a lamp having lead wires which serve assupports for a. filament and Fig. 2 Ais a curve showing the relativeexpansion of the present lead wire and that of soft glass.

A wire of the character above described may be employed as lead wires 8and 9 for a filament I0'of an incandescent electric lamp Il. The leadWire may be sealed through the wall of the bulb by means of a press I2of what is known as soft glass. The press is part of a nare tube I3sealed at I4 to the bulb neck in the usual manner.

It will be noted that the present wire extends through the press and iscontinuous to provide the support members for the filament, making itunnecessary to use an extra section for wetting to the glass.

In Fig. 2 of the drawing, the curve I5 in full lines indicates theexpansion of the lead-wire in increments in length in microns percentimeter at different temperatures. The curve I6 in dotted linesindicates the expansion of the glass measured by the same unit.

When using copper-clad nickel iron wire it was necessary to not onlyconsider the longitudinal coeilicient of expansion but the radialcoefficient as well- The radial coefficient of expansion of copper-cladwire known as Dumet is about the same as that of the present wire, Thelongitudinal coefficient of expansion of the copperclad wire isdifferent, with the result that strains are set up and fine cracks occurabout the seal. Since the present wire and the glass in which it issealed have the same coefcients of expansion in all directions asindicated by the curves, a more practical and effective result isobtained.

It has been found that when an alloy of :about 50% of nickel and theremaining percentage of iron with several other ingredients, theproportions of which will hereinafter be given, is sealed to glasseswhich are known in the art as soft glasses an effective seal is obtainedand such a seal is maintained through a range of temperatures greaterthan that possible with other known seal materials under the bestconditions. A leading-in conductor may, in accordance with the presentinvention, be made in the form of an alloy including the following:

, Per cent Nickel, about 50 Carbon, less than 0.1 Manganese, from about.3 to .5 Silicon, less than .l5 Cobalt Free Iron Remainder The aboveproportionsgive a practical and satisfactory composition althoughslightly larger percentages of carbon and silicon will not change thealloy to such a degree as to make it impractical.

The above formula calls for a cobalt free alloy.

By free is meant without the presence of cobalt in sufficient quantityto detrimentally aiect the coeflicient of expansion of the nickel whenused for the purpose intended. It has been found that up to about onepercent cobalt may be added to the nickel making what is termed to 51percent nickel. Preferably the nickel should contain the least amount ofcobalt possible.

I have found by first removing the normally occluded gases from an alloyas given above, a leading-in conductor may be had which meets allpractical requirements and is superior to and less costly than similarconductors as heretofore employed. For the purposel of removing thegases from the alloy, it is given a heat treatment r at about 1000 to1100 degrees centigrade in. hydrogen. The time interval of treatment is:dependent on the size of the material; that is, sufiicient time shouldbe given to raise the temperature throughout the alloy to thetemperature zone in which itis treated.

The heat treatment frees the metal of gases so that when sealed in aglass wall no gas bubbles occur and' the metal is in intimate andsealtightcontact with the glass. It has .been found that the coefficientof expansion for an alloy given above follows that of such glass aspotassium, lead and barium boro-silicateA over a range of temperaturefrom normal room temperatureup to 450 degrees C.

A leading-in wire made in accordance with the present invention followsthe coeilicients of expansion of the glasses mentioned from roomtemperature to their annealing points, which is important in thatresidual strains can be removed from the glass without breaking the sealby the heat necessary for the annealing operation after the seal ismade.

By reason of the present invention it is possible to make what'is termeda straight-through lead wire having'ythe necessary sealing propertiesand producible at relatively low cost without sacricing any of theproperties necessary to obtain an effective and practical result.

Although a preferred embodiment of the invention is shown and describedherein, it is to be understood that modications may'be made therein byvariations in the portions of the ingredients employed and that theinvention is only limited to the ingredients and proportions given inthe degree and manner pointed out in the accompanying claims.

What is claimed is:

1. An alloy comprising from 50 to less than 51% of nickel, less than 1%of cobalt, less than .1% of carbon, from about .3% to .5% of manganese,less than .15% of silicon, arrd the remainder iron, freed of normallyoccluded gases by heat treating in hydrogen at about 1000 to 1100 C.,and having a coeflcient of expansion .substantially corresponding withthat of soft glasses between room temperatures and about 450 C., wherebyit is especially adapted for the manufacture of leading-in conductorsfor incandescent electric lamps, the bulbs of which are composed of softglass.

2. An alloy comprising 50 to 51% of nickel and cobalt. the cobalt beingless than 1% of the alloy, not more than 1% of other minor ingredients,and the remainder iron, freed of normally occluded gases by heattreating in hydrogen, and having a coefficient of expansion subystantially corresponding with that of soft glasses between roomtemperatures and about 450 C., whereby it is especially adapted for themanufacture of leading-in conductors for incandescent electric lamps,the bulbs of which are composed of soft glass.

3. An alloy comprising 50 to 51% of nickel and cobalt, the cobalt beingless than 1%v of the not more than 1% of other ingredients, and theremainder iron, and having a coelcient of eX- pansion substantiallycorresponding with that of soft glasses between room temperatures andabout 450 C., whereby it is especially adapted for the manufacture ofleading-in conductors for incandescent electric lamps, the bulbs ofwhich are composed of soft glass.

4. An alloy comprising 50 to 51% of nickel and cobalt, and cobalt beingless than 1% of the alloy. not`more than 1% of other ingredients, andthe remainder iron, and having a coetlicient of expansion approximatelywithin the range of that for soft glasses, whereby it is especiallyadapted for the manufacture of leading-in conductors for incandescentelectric lamps.

5. An article comprising soft glass, and a leading-in conductor sealedthereinto, said conductor being a Wire formed entirely of an alloycomprising 50 to 51% of nickel and cobalt, the cobalt being less than 1%of the alloy, not more than 1% of other ingredients, and the remainderiron, heat treated at a temperature of about 1000 to 1100 C. in hydrogento avoid the formation of bubbles at the seal, and the proportions ofthe ingredients being such that its coefiicient of eX- pansioncorresponds substantially with that for soft glass between roomtemperatures andabout 450 C., thereby adapting it for the formation of aperfect seal in said glass.

6. An article comprising soft glass welded to an alloy of 50 to 51% ofnickel and cobalt, the cobalt being less than 1% ofthe alloy, not morethan 1% of other minor ingredients, and the remainder iron, freed ofnormally occluded gases by heat treating in hydrogen at about 1000 to1100 C., whereby it has a coefiicient of expansion substantiallycorresponding with that of said soft glass between room temperatures andabout 450 C.

7. An essentially strain-free seal consisting of glass in fusedcombination with an alloy comprising 50 to 51% of nickel and cobalt, inwhich the cobalt is less than 1% of the alloy. not more than 1% of otherminor ingredients, and "the remainder of iron. freed of normallyoccluded gases by l0 heat treating in hydrogen at about 1000 to 1100 C.,whereby the thermal expansion characteristics of said glass and alloyare substantially coincident from room temperatures atleast up toapproximatelyl the annealing point of the glass.

8. An article comprising soft glass welded to an alloy containing 50 to51% of nickel and cobait. the cobalt being less than 1% of the alloy,not more than 1% of otherminor ingredients, and the remainder iron, saidglass having a thermal expansion characteristic which substantiallymatches that of the alloy from'room temperature at least up to thesoftening point of the glass.

' JOHN H. RAMAGE.

